The present invention relates to multi-tank fuel storage systems for transportable electric generators. More particularly, the invention relates to flexible capacity, multi-tank fuel storage systems for refrigerated freight containers. The multi-tank fuel storage system is usable with containers that are transported by truck in either the underslung or the clip-on mode, as well as containers which are transported by rail or ship.
Refrigerated freight containers which are transportable by truck, rail, and, ship are well known in the art. Electric generator units which attach either to a chassis transporting such a container, or which attach directly to the refrigerated freight containers to provide the necessary power are also known in the art. Indeed, standards for such refrigerated freight containers and their attachments have been promulgated by ANSI and ISO and specify loads, fittings, and clearances to be used with containers utilized in international commerce.
Those skilled in the art will recognize that different requirements present themselves for each mode of transportation of the containers. For example, in the railroad mode, a higher fore and aft load requirement is necessary than on ship due to coupling forces which occur during reclassification of railcars. In the ship mode, to permit stacking and/or proper loading it is preferable that the generator unit housings not extend above the top plane of the refrigerated container. In the truck mode, if the generator housing is mounted to the front of the container ("clip-on"), it is necessary to provide swing clearance for the tractor pulling the chassis mounted container. If the generator housing is mounted to the chassis ("underslung"), a sufficient ground clearance is necessary to prevent damage from road hazards. Because of these different requirements, the industry initially provided some refrigerated containers which were particularly arranged to be equipped with underslung generators, and other containers which were particularly arranged to be equipped with clip-on generators. However, this lack of uniformity forced the operators to maintain two incompatible sets of generators which led to unacceptable expenses and complications, in order to overcome these difficulties, a combination unit which could be used in either the underslung or clip-on mode was provided by the inventor hereof. Details of that combination unit are provided in U.S. Pat. No. 4,732,360, which is hereby incorporated by reference herein.
Another difficulty which has been encountered by the art concerns the fuel storage capacity of the generator unit system. Two alternatives are generally available. A first system stores fuel in a fuel tank integral to the generator unit housing; typically in a storage area formed by the base of the housing. In order to have a large fuel supply, the base must be designed with a large storage area which may not be necessary for short trips and which is only occasionally fully used for long distance trips. Also, as the storage area is increased, compatibility with different modes of transportation, and different container arrangements decreases. In particular, because the storage area is increased by substantially increasing the depth of the base (the width being substantially preset due to other constraints), the unit cannot be used in an underslung arrangement because not enough road clearance is provided. Also, even in the clip-on mode, refrigerator unit control doors may be undesirably blocked.
A second system used in the art stores fuel in a separate tank (see e.g. U.S. Pat. No. 4,732,360, previously incorporated herein) which is coupled to the generator via appropriate hoses. While this system is a little more flexible than the integral tank storage system, as different sized tanks may be switched in and out as desired, the system still suffers from the fact that if the separate tank is carried in the underslung mode, the capacity is limited due to road clearance problems. Moreover, the switching of tanks and the use of large capacity tanks is undesirable from an operation standpoint because additional equipment is required, and the maintaining of a range of tank sizes is undesirable from a financial standpoint.